This invention relates generally as indicated to a continuous strip accumulator, and more particularly to an improved accumulator apparatus for storing in an expanding and contracting spiral a length of strip material received from a source of supply and feeding such strip material to a mill, machine or other apparatus without interruption while the source of supply is being replenished.
Continuous strip accumulators of various types have previously been provided for storing a length of strip material in an expanding and contracting spiral coil having a fixed number of turns with the strip material being fed to the inside of the spiral coil and withdrawn from the outside or vice versa. One such accumulator which has operated satisfactorily is disclosed in U.S. Pat. No. 3,860,188. However, one drawback of this type of accumulator is that all of the drive rolls and pinch rolls are independently driven by separate D.C. motors which, together with their associated electrical controls, add considerably to the overall cost and complexity of the accumulator as well as the maintenance thereof. Also, a dancer roll is normally required to provide a feedback signal to the drive motor for the entry pinch rolls to regulate the speed of the incoming strip, which further adds to the cost and complexity of the accumulator.
The drive rolls for supporting the spiral coil in previous known accumulators are also usually inclined and/or skewed to assist in the expansion of the coil during the filling operation, and are usually solid hardened ground rolls which are not only quite costly, but add considerably to the weight of the accumulator. The skewed drive rolls also result in a change of the angle of the strip material to the rolls with each convolution, causing a different velocity relationship for each convolution. Moreover, the drive rolls normally are continuously driven during contraction of the spiral coil, thus necessitating the provision of several lifting stations around the inner periphery of the accumulator and associated controls for successively lifting the convolutions off the drive rolls after they have been contracted, which further adds to the cost of the accumulator and requires additional maintenance.
Another objection to such prior accumulators is that during expansion and contraction of the spiral coil within such accumulators, that portion of the strip material being expanded or contracted is substantially unsupported, thus making such operation rather delicate. Also, because of such lack of support, there is considerable contact surface pressure between convolutions, thus necessitating that the strip material be put under increased tension during the filling mode to overcome such pressure.